how do I leave someone else’s share without leaving call

Hello tristen60,

Thank you for reaching out in Apple Support Communities. You would need to ask the individual who's sharing their screen in FaceTime to end screen sharing. That way you will no longer view their screen. Here's how to end screen sharing in FaceTime:

"End a screen sharing session

At the top of the FaceTime call, tap the Share Content button  again to stop sharing your screen."

That information is outlined here: Share your screen in FaceTime on your iPhone or iPad

You can also view this helpful YouTube video by Apple Support on how to end screen sharing in FaceTime. You can fast forward to the 43rd second of the video of how to end screen sharing: How to share your screen in FaceTime on iPhone and iPad | Apple Support

If we misunderstood, please provide the community additional details. That way we can gain a better understanding and provide you the best support.

Kind regards.